Hi Francis,
Could you confirm that the Zenmuse XT camera was selected in the (iOS) General settings of the app?
The issue you are mentioning could be related to the Picture capture fail issue that some other users are experiencing. As mentioned in the community post, we recommend formatting the SD card before the mission, switching to the camera view to see if the video feed is working and “blinking” when the image is captured. There is also an SD card memory indicator in the telemetry menu of the Pix4Dcapture app that can be used as an indication if the images are actually captured.
Since we do not expect this issue to be systematic for every mission we recommend to abort the mission and plan/fly it again.
Also, have a look at this article as it might answer questions related to the configuration you use: (Android, iOS) Pix4Dcapture and DJI Zenmuse XT.
Best,